Aerosol dispensers are well known in the art. Aerosol dispensers typically comprise an outer container which acts as a frame for the remaining components and as a pressure vessel for propellant and product contained therein. Outer containers made of metal are well known in the art. However, metal containers can be undesirable due to high cost and limited recyclability. Thus, plastic outer containers may be utilized for aerosol dispensers.
The outer containers are typically, but not necessarily, cylindrical. The outer container may comprise a bottom for resting on horizontal surfaces such as shelves, countertops, tables etc. The bottom of the outer container may comprise a re-entrant portion as shown in U.S. Pat. No. 3,403,804. Sidewalls defining the shape of the outer container extend upwardly from the bottom to an open top.
The open top defines a neck having an opening for receiving additional components of the aerosol dispenser. The industry has generally settled upon a neck diameter of 2.54 cm, for standardization of components among various manufacturers, although smaller diameters, such as 20 mm, are also used. Various neck shapes are shown in US 2007/02782531 A1; U.S. Pat. Nos. 7,303,087; 7,028,866; and commonly assigned U.S. Pat. No. 6,019,252.
Typically a valve cup is inserted into the neck. The valve cup is sealed against the neck to prevent the escape of the propellant and loss of pressurization. The valve cup holds the valve components which are movable in relationship to the balance of the aerosol dispenser.
Aerosol dispensers, having a valve cup and movable valve components, may comprise different embodiments for holding, storing, and dispensing product used by the consumer. In one embodiment, the product and propellant are intermixed. When the user actuates the valve, the product and propellant are dispensed together. This embodiment may utilize a dip tube. The dip tube takes the product and propellant mixture from the bottom of the outer container. By dispensing from the bottom of the outer container, the user is more likely to achieve dispensing of the product/propellant mixture and not dispense pure propellant from the headspace. This embodiment may be used, for example, to dispense shaving foam products.
In another embodiment, a collapsible, flexible bag may be sealed to the opening on the underside of the valve cup or may be placed between the valve cup and the container. This bag limits or even prevents intermixing of the contents of the bag and the components outside of the bag. Thus, product may be contained in the bag. Propellant may be disposed between the outside of the bag and the inside of the outer container. Upon actuation of the valve, a flow path out of the bag is created. Gage pressure from the propellant disposed between the bag and the outer container causes pressurization of the product, forcing the product to flow into ambient pressure. This embodiment is commonly called a bag on valve or bag in can and may be used, for example, in dispensing shaving gel products. In either embodiment, flow to the ambient may comprise droplets, as used for air fresheners or may comprise deposition on a target surface, as may occur with cleansers.
Both embodiments may utilize hydrocarbon propellant and/or inert gas propellant, such as Tetrafluoroprop-1-ene commercially available from Honeywell Company of Morristown, N.J. or nitrogen. If a hydrocarbon propellant is selected, the manufacturing process often becomes more complex and costly due to safety concerns, environmental regulations and other industry regulations.
Plastic outer containers have the advantages of cost and recyclability. But in order to accommodate the desired pressure during shipment, storage and use, the walls of the outer container must be able to withstand and maintain the gage pressure after manufacture through a variety of temperatures, orientations, and handling by the user. The walls of the container must therefore be thick enough to minimize/prevent leakage/permeation of the contents under pressure or cracking due to stress. This has been accomplished by providing thicker walls. However, relatively thick walls present the problem of material cost and are viewed as environmentally unfriendly.
Attempts to provide various geometries and selective thickness, are shown in U.S. Pat. Nos. 5,152,411; 7,028,866 7,303,087 and in WO 2011/088093. But these approaches have not proven entirely satisfactory. For example, under pressure and with certain product chemistries, including perfumes and organic materials, crazing can occur. Crazing is the appearance of small cleaves in the plastic, resembling cracks. Crazing is undesirable from both an aesthetic and functional point of view.
Another attempt to overcome the problems of pressurized plastic containers is to crystallize the plastic in certain portions of the container as shown in U.S. Pat. Nos. 4,151,250; 4,264,558; 4,385,089; 4,476,170; 4,512,948; 4,522,779; 4,755,404; 4,839,127; 4,871,507; 4,883,631; 5,261,545; 5,419,866; 5,520,877; 5,735,420; 5,759,656; 5,829,614; 5,908,128; 6,168,740; 6,372,318; 6,497,569 a divisional of U.S. Pat. Nos. 6,168,740; 6,514,451; and 6,926,859. But these teachings have been unsatisfactory in showing how to crystallize a plastic aerosol outer container to prevent crazing and other undesirable manufacturing artifacts.